The present invention relates to a needle assembly for collecting fluid such as from a patient, and more particularly, concerns a needle assembly for collecting multiple samples of fluid from a patient with an anti-backflow valve included in the assembly with a provision for indicating the entry of the needle assembly into the vein of the patient.
In the collection of fluids, and especially when such fluids may be blood or other bodily fluids from a patient, it is most desirable that backflow into the patient or other source be prevented. The reasons for prevention of fluid backflow into the patient are numerous. For example, when collecting blood into a collection container, various chemicals or other reagents may be present in the container for different tests on the blood sample. As the blood sample flows into this container, it mixes with the chemical therein. Should this mixture backflow into the patient, the chemical would then enter into the patient's blood stream with potential harm. Another instance where backflow into the patient could be problematical involves clotting of the blood during the collection procedure. Should a small amount of the collected blood clot somewhere in the collection needle or container, backflow of such a clotted or coagulated amount of blood into the patient could cause serious difficulties. Accordingly, the inclusion of some type of anti-backflow device or valve into a needle assembly for the collection of fluids from a patient is a desired feature.
In addition, it is also desirable to provide a mechanism whereby the user of such a needle assembly can be informed when the intravenous needle has penetrated the vein of the patient. Many times in collecting blood from a patient it is difficult to locate the vein or for other reasons blood flow into the collection device is minimal. In these instances, it becomes most advantageous to be able to make a quick determination that entry into the vein has been made and that blood is flowing into the needle assembly. Once this determination has been made and vein entry indeed accomplished, the evacuated blood collection container can then be inserted into the collection assembly in accordance with these well known techniques of collecting multiple blood samples during a single collection procedure.
One of the problems which arises during the venipuncture step concerns the pocket of air which is found in various needle assemblies useful for multiple sample blood collections. When venipuncture is made, and the evacuated blood collection container is not yet attached to the opposite end of the needle structure, blood cannot always flow into the needle assembly because of this pocket of air which, under normal atmospheric conditions, remains inside the needle assembly. Accordingly, even though vein entry may have been accomplished, the blood may not move through the intravenous needle into the collection assembly under tourniquet pressure until the evacuated blood collection container is attached, whereupon the vacuum source causes sufficient draw through the needle assembly. In a previously filed patent application entitled "Blood Sampling Assembly Having Vein Entry Indicator" by William N. Eldridge, U.S. Ser. No. 915,670, filed June 15, 1978, and assigned to the common assignee herewith, the inventor recognized that this air blockage problem prevented the blood from flowing through the intravenous needle to a point where it could be seen by a user. In the Eldridge invention, a porous vent means is provided in conjunction with a one-way valve whereby air inside the needle assembly is allowed to pass out of this venting means during the initial stages of the blood collection procedure. However, the venting means prevents the passage of blood for at least a reasonable amount of time, such as may be long enough for the user to attach the evacuated blood collection container to the needle assembly. Once the negative pressure of the evacuated blood collection container is attached, the one-way valve opens up and allows blood to travel from the vein of the patient, through the needle assembly and on into the container.
Although the Eldridge invention is most advantageous in providing the combination one-way valve and air venting means, there is still room for improvement thereover. The present invention is directed to improving the type of combination in a needle assembly suggested by Eldridge.